I’d suggest having the guy walk (roll) around the box, do a complete circuit. Look it up and down. Pause somewhere, as if thinking… then very slowly edge towards it… But as he does so the box moves a little… and the guy jumps back. He edges back again… (or not depending upon how brave he feels ) then carefully edges forward again… this time getting really close… then just when he is about to touch the box it really jumps around (maybe use a lattice to the box and stretch it around)… the little guy runs off hits the wall… spins around very fast and erratically and then colapses in a heap, backwards and the bottom bit jiggles a bit (nervous twitch). There is a pause. The box stretches up as if to see if the guy is alright, then does the joke flag thing. This is just my thoughts, use them as you will.